So here's the timeline that lead to Mami's suspicions.
https://e-hentai.org/s/3d8a771db2/2032531-5
Sees Suma eating a "cute" homemade bento.
https://e-hentai.org/s/c0bf9d097a/2245770-12
Recognizes Karin's bento box.
https://e-hentai.org/s/0a8b3b23710d6f228a1b6751ccf4efdf0516d865-672934-936-1330-jpg/2350218-16
Hears people doing it in the prep room.

But as long as Suma doesn't get flustered and drop the all it should be... Oh. Right.

Raws taken from:
https://e-hentai.org/g/2484478/dc3c538d44/
uploaded by:
https://e-hentai.org/uploader/hobohobo

ntr time, teacher gonna get blackmail to fuck other girl.

Base +8, evaluv3r999 +5, Seaea. +6, Narutlih -6

*drops the ball. Sorry.

Base +7

Mami is going to blackmail him to get on his dick, isn't? She is really thirsty... I hope Suma doesn't fall for it.

Base +6

All the boys think Amuro will fuck anyone now, and slut girl knows about them, will use that to try to get with Suma, if that happens, Amuro will be mad. Ryoh-zoh, has it reached that point for it all to come crashing down? NTR incoming? Also confirmed Hori was the one getting fucked by the rando last chap

Base +6

The guy who fucked Hori in chapter 17 was Mami's boyfriend, I think.

Base +21

yep, it's going into NTR route i guess. Amuro probably will get fucked around because of the new rumors while Suma are helpless because Mami

Base +6, HakuWillReturn -6

NTR back to menu???

Base +13, evaluv3r999 +5

I mean the ’teacher‘ section isnt fun finally end it

Base +4

现在是ntr吗？现在看起来没有啊

Base +6

↑目前没有NTR，但是最后三张可以看出来，下一话可能会有转折。
I hope they have a happy ending😭🙏🏻

Base +4, APepper -6